But it's tissue-thin paper which already has its surface covered in now useless information. Also, the paper is likely glossy now (from the weight of the rest of the phonebook), rendering what little space is left on it useless for writing.

This. I was also thinking maybe one could argue the layout of your hometown would be greatly changed by a nuclear bomb going off in it. But then... I would also think roadsigns are the first to be ******* vaporized so what good would addresses be then.